Functional capabilities of synaptic terminals can be studied with morphologic methods. Terminals are subject to astructural alteration in response to normally occurring biological events such as gene action and development. Some features can be studied with biochemical markers which can subsequently be visualized autoradiographically and histochemically. The objectives of this study are: 1) to analyze the basic structure of auditory terminals and their distribution on identified cells; 2) to correlate the structure with biochemical characteristics of terminals demonstrated morphologically; and 3) to study gene action on selected terminals. Such information will enhance our understanding of the morphorlogical bases for physiological events in the information processing capabilities of these nuclei. Terminals in the medial superior olivary nucleus (MSO) and other brain stem auditory nuclei will be studied because of the features (including the presence of an intercellular substance) common to some classes of auditory terminals and the distribution of collaterals of auditory axons to these nuclei. Normal kittens, cats and inbreed mice (C57B1/6, FS/EI and Shaker 1) will be used. Electron microscopic analysis of Golgi material will be used to study the distribution of specific synaptic terminal classes on identified cells. Horseradish peroxidase labeled and I125 labeled alpha-bungarotoxin will be used to localize acetycholine receptor sites in auditory nuclei. Uptake of H3-GABA and H3-glycine by auditory neurons and terminals will be studied in brain stem slices. Electron microscope histochemistry and autoradiography will be used to study relationships between terminals and their internal and surrounding structures.